Fire in Atlanta 3

[dik]

From the AP, " A large fire has caused an overpass on Interstate 85 to collapse in Atlanta.

WSB-TV reports the massive blaze is burning underneath I-85 northbound near Piedmont Road. It has shut down several roads in northeast Atlanta.

Witnesses say troopers were telling cars to turn around on the bridge because they were concerned about its integrity. Minutes later, the bridge collapsed."

Dik

 

[oldestguy]

This is not an engineering failure, since fire proofing bridges is not normally required for their integrity. Also that may fail if damaged by the vehicle underneath. World Trade Center disaster was due to fire proofing failure by damage from plane.

 

[hokie66]

Whether it is an engineering failure or not, I85 is closed, probably for a long time. Big problem.

 

[berkshire]

Apparently there was a fenced in compound under the bridge at that point, containing spools of what appears to be Polyethylene gas pipe. A large quantity.
B.E.

You are judged not by what you know, but by what you can do.

 

[MintJulep]

Recall similar fire in Philadelphia years ago.

http://www.philly.com/philly/blogs/...re-recalls-Philly-I-95-fire-21-years-ago.html

 

[RobertHale]

I am pretty confident it was underground fiber-optic conduit on spools (not sure if it was just bare conduit). I also think it was GDOT's yard.

Robert Hale, PE

 

[JG2828]

Here are some photos of what was stored under the bridge. As found on the internet.
You can have a look on Google Street View yourself here:

https://www.google.com/maps/@33.813...KgMNYjAeg8EoFVt14Q!2e0!7i13312!8i6656!6m1!1e1

 

[itsmoked]

It's so enticing to store stuff under these massive weatherproof concrete umbrellas but what an expensive disaster when any of it burns. Makes me think of good old fire-happy Oakland where for miles the elevated freeway is over shanty-towns, auto-wrecking yards, industrial equipment piles, warehouses, garages, bus storage, abandoned buildings, etc., etc.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[dik]

Good thing that Oakland doesn't have fires...

 

[BrianPetersen]

Can't find much on the internet about it, but in 1986, a gasoline tanker was involved in a collision and caught fire on Ontario Highway 401 directly underneath the James Snow Parkway bridge (exit 324). A temporary detour for the highway was constructed very quickly - if I remember right, within a week. But, this happened long before significant commercial development all around that area, and it would be a much bigger challenge to do the same today, and certainly a huge challenge to do this in Atlanta.

 

[itsmoked]

Remember this?
[URL unfurl="true"]http://www.cbsnews.com/news/tanker-fire-causes-ca-highway-collapse/[/url]

Keith Cress
kcress -

http://www.flaminsystems.com

 

[JAE]

I found a few quotes interesting on this:

[red]Experts in structural engineering said fires on highways and bridges rarely burn long enough or hot enough to cause a complete collapse — but it has happened. Intense heat can compromise even steel-reinforced concrete, said Lauren Stewart, director of the Structural Engineering and Materials Laboratory at Georgia Tech in Atlanta.[/red]
It is SO nice to have a reference to "structural engineering" instead of "An Architect stated...."

[red]McMurry said his department stored coils of plastic conduit, used in fiber optic networks, beneath the span but insisted they were noncombustible.[/red]
So if these coils were non-combustible, what the heck fueled such a hot fire?

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[oldestguy]

Looking at the photos and if I was a homeless guy (we used to call them tramps) that site looks mighty appealing for a hang out. Nice roof too. Move a few piles and set up your camp. Maybe start a small camp fire for warmth or heating that coffee you scrounged from down the road. Gosh, I didn't know that stuff would burn.

 

[JAE]

They've actually arrested and charged a guy with starting the fire.

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[BrianPetersen]

"Non-combustible" or "self-extinguishing" might be true if you try to burn an individual piece of that plastic, but an entire mass of it can be a different story. The Mont Blanc tunnel fire disaster in 1999 involved a truck carrying margarine, which one wouldn't normally think of as a hazardous material, but it contains more or less the same energy content as oil.

 

[JedClampett]

The sound you hear is highway departments from coast to coast making sure they don't stage any HDPE under their bridges.
So the next fire will be of something slightly different. Like PE

 

[TehMightyEngineer]

I wonder if the cables were lubricated for ease of pulling. Wouldn't surprise me if that was what burned and was hot enough to sustain all the other combustibles plastics in the area. I'd also think coils of tube would make great chimneys to direct fire upward.

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

https://www.facebook.com/AmericanConcrete/

 

[JohnMcNutt]

Can't see much in that area but speculating here: don't forget the wood spools, wood pallets, and who knows what other material; cardboard boxes, tarps, etc. likely in the area.

 

[Lnewqban]

What could have been the source of the heavy black smoke prior to the collapse?

"Where the spirit does not work with the hand, there is no art." - Leonardo da Vinci

 

[BrianPetersen]

Plastic heated to its melting / decomposition temperature is just like any other hydrocarbon, and when burning in a situation where heat is in ample supply and oxygen is in short supply, it's gonna be a black smoker.